Biochemistry Questions and Answers – G Protein – Coupled Receptors and Second Messengers

This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “G Protein – Coupled Receptors and Second Messengers”.

1. Which out of the following statements is true about G-protein couple receptors?
a) The N-terminal chain is extracellular and C-terminal chain is intracellular
b) It contains 5 trans-membrane hydrophobic sections
c) There are more extracellular loops than intracellular loops
d) The binding region for G-protein involves 2 extracellular loops
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2. Which of the following is not a G-protein coupled receptor?
a) Glycine receptor
b) Adrenergic receptor
c) Glutamate receptor
d) Muscarinic receptor
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3. Protein kinase A is ____________
a) Completely inhibited by cyclic AMP
b) Allosterically activated by cyclic AMP
c) Affected by cyclic AMP only under unusual circumstances
d) Activated by covalent binding of cyclic AMP
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4. Which out of the following is not involved in signal transduction by β-adrenergic receptor pathway?
a) GTP
b) ATP
c) cAMP
d) cGMP
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5. Which of the following catalyzes the cutting of PIP2 into 2 moles of IP3 and diacylglycerol in cell signaling?
a) Phosphokinase C
b) Phospholipase C
c) Lipokinase
d) Phosphodiesterase C
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6. The binding of ligands to many GPCRs leads to ___________
a) Decrease in concentration of certain intracellular signal molecules called second messengers
b) Increase in concentration of certain intracellular signal molecules called second messengers
c) Decrease in concentration of certain extracellular signal molecules called first messengers
d) Increase in concentration of certain extracellular signal molecules called first messengers
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7. A hormone or ligand can be considered as ___________
a) First messenger
b) Second messenger
c) Third messenger
d) Fourth messenger
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8. Which of the following serves as a neurotransmitter in adrenergic neurons?
a) Serotonin
b) Epinephrine
c) Dopamine
d) Histamine
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9. Which second messenger signals the release of Ca⁺² from endoplasmic reticulum?
a) IP3
b) 1, 2 diacyl glycerol
c) cAMP
d) cGMP
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10. GPCR is comprised of ___________
a) 7 transmembrane helices
b) 8 transmembrane helices
c) 9 transmembrane helices
d) 10 transmembrane helices
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